WASHINGTON — Senator Mitch McConnell is about to plunge the Senate into the nation’s culture wars with votes on bills to sharply restrict access to late-term abortions and threaten some doctors who perform them with criminal penalties, signaling that Republicans plan to make curbing a woman’s right to terminate a pregnancy a central theme of their re-election campaigns this year.

After months of shunning legislative activity in favor of confirming President Trump’s judicial nominees — and a brief detour for the president’s impeachment trial — Mr. McConnell, Republican of Kentucky and the majority leader, is expected to bring the bills up for votes on Tuesday. Both lack the necessary 60-vote supermajority to advance, and the Senate has voted previously to reject them.

But by putting them on the floor again, Mr. McConnell hopes to energize the social conservatives who helped elect Mr. Trump and whose enthusiasm will be needed to help Republicans hold on to the Senate this year, while forcing vulnerable Democrats to take uncomfortable votes on bills that frame abortion as infanticide. The rhetoric around the measures is hot; Mr. Trump, for instance, has pointed to one of the bills to falsely assert that Democrats favor “executing babies AFTER birth.”

Mr. McConnell declined to be interviewed, though in past speeches he has said the legislation poses “moral questions” that Democrats must answer. And on Monday, noting that only seven countries allow the procedure after 20 weeks of pregnancy, he said the late-term abortion ban would “bring our nation’s regard for the unborn off this sad and radical fringe and bring it more in line with the global mainstream.”