With the Supreme Court term expected to end by Thursday, a string of high-profile rulings had shattered the consensus that marked the early days of the Roberts court while casting preliminary doubt on whether the fears of opponents over how the two newest justices would make their decisions were justified.

The court yesterday struck down Vermont’s state campaign finance laws and upheld Kansas’s state death-penalty statute. The justices are widely expected to hand down rulings later this week in cases involving detention of terror suspects at Guantanamo Bay and congressional redistricting in Texas.

In recent weeks, they have also ruled in cases touching on whistleblower protections for government employees, rules governing police searches, application of the Clean Water Act, and interpretation of workplace anti-discrimination laws.

The end results of many of those cases have alarmed some who had opposed the confirmations of Justices Roberts and Alito. But complicated voting splits among the justices on some of the rulings provide opportunities to discern differences between the new justices and their conservative colleagues.

In the Vermont case, Randall et al. v. Sorrell et al., the court voted 6-3 that Vermont’s 1997 campaign finance law imposed unconstitutional limits of both contributions and spending, but the majority fractured in explaining the basis for its decision.

In the Kansas case, Kansas v. Marsh, the court ruled 5-4 that Kansas’s death penalty statute is constitutional in the face of a challenge to the way it balances aggravating and mitigating factors in sentencing decisions.

Justice Alito was the swing vote in the Kansas case, and the fact that the case was reheard after he joined the court suggests the other eight justices had been tied.

The conflicting majority opinions in the Vermont ruling suggest that the new justices are not moving in lockstep with Justices Thomas and Scalia, as many on the political left had said they would.

Justice Breyer, in a plurality opinion joined in whole by Chief Justice Roberts and in part by Justice Alito, wrote that earlier precedent, especially the court’s 1976 decision in Buckley v. Valeo, opened the door for some contribution limits, but that Vermont’s spending limits were unconstitutional and its contribution limits were too strict.

In joining Justice Breyer’s opinion, the chief justice and Justice Alito stand opposed to their three most conservative colleagues. Justice Thomas penned an opinion, joined by Justice Scalia, saying that although the court was correct to overturn the Vermont statute, Justice Breyer’s plurality opinion was wrong to suggest that even a more permissive regulation would be constitutional. Justice Kennedy filed his own concurring opinion agreeing with the outcome but echoing concerns similar to those of Justice Thomas.

Justice Kennedy questioned whether the court was equipped to set the boundaries between a constitutional and an unconstitutional limit. “On a routine, operational level,” he wrote, “the present system requires us to explain why $200 is too restrictive a limit while $1,500 is not. Our own experience gives us little basis to make these judgments, and certainly no traditional or well-established body of law exists to offer guidance.”

The new justices appeared more willing to rely on stare decisis, the legal doctrine that courts should try to uphold their earlier rulings in the interest of legal stability.

All six justices in the majority agreed that spending limits are unconstitutional, affirming a central finding in Buckley.

Vermont’s attorney general, William Sorrell, described the ruling as “a bitter pill” in an interview with The New York Sun and said the state’s legislature is likely to try to re-craft the state’s contribution limits when lawmakers return in January.

A lawyer who argued on behalf of those challenging the Vermont law, James Bopp, said the outcome suggests the court is pulling away from its embrace of campaign finance restrictions in McConnell v. FEC three years ago.

“This case puts us on a different road,” Mr. Bopp told the Sun.

In the Kansas case, the court focused on the constitutionality of a Kansas statute requiring the death penalty in instances where juries find that mitigating factors precisely balance aggravating factors.

Writing for the majority, Justice Thomas said: “Our precedents establish that a State enjoys a range of discretion in imposing the death penalty, including the manner in which aggravating and mitigating circumstances are to be weighed.”

In a dissenting opinion, Justice Souter wrote that the increasing use of DNA evidence to establish guilt or innocence in capital cases suggests that courts should narrow as much as possible the application of the death penalty. Justice Thomas called that consideration irrelevant to the legal question posed by the case.

The majority in the case consisted of Justices Thomas, Scalia, Kennedy, Alito, and Chief Justice Roberts, all five of whom are Roman Catholic. The Catholic church strongly opposes the death penalty.

With a few days remaining in the term, observers yesterday started weighing in on the first few months for Chief Justice Roberts and Justice Alito.

The general counsel of the conservative Committee for Justice, Curt Levey, praised the new justices, whom Mr. Levey’s organization supported during their confirmation proceedings, saying that conservatives are generally happy with the justices.

“They have been reliable constitutionalists,” Mr. Levey told the Sun. “They certainly haven’t done anything radical yet.”

The vice president of People for the American Way, Elliot Mincberg, was more guarded in his assessment. Mr. Mincberg’s group opposed the nominees.

It’s “obviously a little early to tell” how the new justices will turn out, Mr. Mincberg told the Sun.

Mr. Mincberg sees the new justices trying to exert a rightward pull on the court but that Justice Kennedy has held them back in key cases.

A constitutional scholar at the American Enterprise Institute, Michael Greve, also pointed to the consensus the justices have built on many rulings this term.

The most striking aspect of the past two weeks has been the apparent dissolution of that consensus, Mr. Greve said, although he says it is hard to predict what that might presage.

All three caution that it is too soon to find any clear patterns in respect of questions like respect for precedent. A final verdict on this term will need to wait for rulings in the Texas and Guantanamo cases.

Ultimately, the real test may come next term, in which Chief Justice Roberts and Justice Alito will have participated more in deciding which cases to hear. The court has already announced that it will take up cases involving abortion and school desegregation.

Also yesterday, the court agreed to hear a case on whether states can force the Environmental Protection Agency to regulate carbon dioxide emissions and declined to hear a drug patent case dispute and a challenge to states that offer optional car license plates with messages opposing abortion.