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Carlos Osorio, Associated Press
First lady Michelle Obama stands with Michigan gubernatorial candidate Mark Schauer, left, and Senate candidate, Rep. Gary Peters during a campaign rally for them in Detroit, Friday, Oct. 10, 2014. Michelle Obama came to heavily Democratic Detroit Friday afternoon to rally support for Peters, a suburban Detroit congressman hoping to succeed retiring Democrat Sen. Carl Levin after 36 years in office.

DES MOINES, Iowa — Democratic candidates in Iowa and Michigan for hotly-contested open U.S. Senate seats got a charisma boost Friday from the White House.

Not from the commander in chief, but his more popular wife.

Michelle Obama campaigned in Des Moines for Rep. Bruce Braley, who critics say is losing the personality war to Republican Joni Ernst, a likable state Senator who has touted her farm upbringing and military background.

Earlier in the day, the first lady stopped in heavily Democratic Detroit to support Rep. Gary Peters, who is leading in the polls for an open Michigan seat against Republican Terri Lynn Land.

Before a crowd of about 1,200 at Drake University, Obama urged supporters to vote early in the Iowa race that is one of the closest in the nation and is viewed as crucial if Democrats hopes to stave off a Republican drive for a six-seat gain to take a Senate majority.

"When we stay home, they win. They're assuming that we won't care. They're hoping that we're not organized and energized and only we can prove them wrong," Obama said of Democrats, whose partisans tend not to turn out as enthusiastically in midterm elections.

The first lady has become something of a campaigner-in-chief, most recently for Midwest candidates also including Wisconsin and Illinois. She drew an enthusiastic response in Des Moines, though she mispronounced the name Braley (BRAY'-lee) — leaving out the "r'' — several times and was finally corrected by the audience.

"I've been traveling too much," Obama said contritely.

Obama also referred to Braley as a Marine Corps veteran, which he is not. Braley's staff said she meant to refer to Braley's late father, who served in the marines. His opponent Ernst is a lieutenant colonel in the Iowa National Guard.

In Detroit, Obama stumped for Peters and Democratic gubernatorial challenger Mark Schauer, a congressman from 2009-11. The race is tight though some recent polls show GOP Gov. Rick Snyder with a slight edge.

"It really boils down to one fundamental truth: Gary and Mark ... understand what Michigan families are going through," Obama said. "They are going to be on your side every single day out in Lansing and in Washington, D.C."

Obama drew a rousing response from the audience in Detroit, the largest municipality in the United States to file for bankruptcy and also home to the rebounding domestic auto industry.

Democrats have sought the first lady's help even though many have avoided appearing with her husband, whose job approval rating has sunk to the low 40s. She is viewed positively by 62 percent of the public, according to the most recent Pew Research Center survey.

She's not the only high-profile Democrat to be crisscrossing the country in the campaign's final weeks. Hillary Rodham Clinton, a potential 2016 presidential candidate, has announced plans to campaign in at least 10 key states.

Republicans are doing the same. Mitt Romney plans to campaign in Iowa with Ernst on Sunday and Monday. Former Florida Gov. Jeb Bush, another possible presidential contender, plans to make stops across Michigan on Monday that include a Republican party fundraiser with Snyder.