In a rare fit of realism on Tuesday, Senator Mitch McConnell, the Republican leader, admitted he would be unable to repeal the Affordable Care Act if Republicans win the Senate next week and he becomes majority leader. That would take 60 votes, he said, and no one thinks Republicans will get that many.

But conservatives reacted with anger to what they considered a demonstration of weakness, and on Thursday Mr. McConnell was forced to backtrack. Yes, his spokesman told The Washington Examiner, Mr. McConnell remains “committed to the full repeal of Obamacare” with only a simple majority, through a parliamentary procedure known as reconciliation.

Those two comments are a pretty good indication of what life will be like in Congress if Republicans gain control of the Senate in Tuesday’s election, and if Mr. McConnell wins his race in Kentucky. It’s not just that they are committed to time-wasting, obstructionist promises like repeal of health care reform, which everyone knows President Obama would veto. The bigger problem is that the party’s leaders have continually proved unable to resist pressure from the radical right, which may very well grow in the next session of Congress.

Tea Party loyalists like Senator Ted Cruz of Texas already have far too much sway over the Republican caucus, but if they become the majority, things could become worse. The Republican Senate candidate in Iowa, Joni Ernst, wants to ban abortions and same-sex marriage and impeach the president. In Georgia, David Perdue, the Republican candidate, said his biggest task is to “prosecute the failed record” of the Obama administration. Senator Pat Roberts of Kansas, a three-term incumbent in a tough race for re-election, promised voters that a Republican majority “means a stop to the Obama agenda.”