(Reuters) - Republican Senate candidates in tight races in Indiana and Arizona have begun featuring endorsements from Mitt Romney following the Republican presidential candidate's rise in the polls, campaigns said.
Indiana Senate candidate Richard Mourdock on Monday launched a television and radio ad statewide that features Romney endorsing the conservative state treasurer in a tight race against Democratic congressman Joe Donnelly.
"This fall, I'm supporting Richard Mourdock for Senate," Romney says in the ad. "As Senator, Richard will be the 51st vote to repeal and replace government-run healthcare."
Republicans need a net gain of four seats to take the majority in the Senate from Democrats, or three seats if Romney is elected president. Romney has said that if elected he would ask Congress to repeal President Barack Obama's health care law.
In Arizona, Romney did a 52-second autodial call on behalf of Republican Senate candidate Jeff Flake that went out on Saturday, saying "the stakes could not be higher for Jeff's election." Flake faces a surprisingly strong campaign from Democratic candidate Richard Carmona, a former surgeon general.
The Romney call went out to Republicans statewide, plus a chunk of Democrats and independents, the Flake campaign said.
Flake's campaign said the Romney spot will help drive efforts to get out the vote in Arizona.
Both Mourdock and Flake are strong conservatives struggling to put some distance between themselves and Democratic opponents. Until now, most Senate candidates had kept Romney at arms length because he had trailed Obama in national polls for months.
But Romney has made gains since the first presidential debate on October 3. Both Indiana and Arizona lean toward Romney in the presidential race, according to recent polls.
(Reporting By Greg McCune; editing by Todd Eastham)