Democrats badly want to get back control of the Republican-controlled Senate in the Nov. 8 election.
Democrats badly want to get back control of the Republican-controlled Senate in the Nov. 8 election, and are sending Obama, Michelle Obama and Joe Biden to states where close races could tip the balance.
In Nevada, Obama reserved most of his firepower for mocking three-term Republican U.S. Representative Joe Heck, who had supported his party's presidential candidate until earlier this month when Donald Trump's campaign went into crisis mode by the release of a video in which he lewdly bragged about groping and kissing women.
"I understand Joe Heck now wishes he never said those things about Donald Trump, but they're on tape, they're on the record," Obama said, using Heck's earlier praise of Trump against him.
It was Obama's second consecutive campaign rally where he spent as much time talking about the Senate as he did about Clinton's race.
Three days ago, Obama excoriated Republican Senator Marco Rubio of Florida - who has a narrow lead over Democratic challenger Patrick Murphy, a congressman - for failing to repudiate Trump.
Obama won Nevada in 2008 and 2012. Polls show Clinton with a 4.2 percentage point lead at 45.4 percent support to Trump's 41.3 percent, according to the RealClearPolitics average.
The Nevada Senate seat is the only Senate race this year that Republicans could flip to their control. The seat has long been held by Harry Reid, the Senate Democratic leader, who is retiring.
Obama was introduced by the Democratic Senate candidate Catherine Cortez Masto, a two-term Nevada attorney general, who would be the first Latina elected to the U.S Senate if she wins.
"We can't elect Hillary and then saddle her with a Congress that is do-nothing, won't even try to do something," Obama said.
Cortez Masto currently has a slim 2.3 percentage point lead in an average of polls tracked by RealClearPolitics over Heck.
Reid has complained that "outside money" from his long-time foes Charles and David Koch has poured into the race.
"Her opponent's going to have Koch brothers on line one and Donald Trump on line two," Obama said.
In the final two weeks leading up to Nov. 8, Clinton said she planned to work hard to support congressional and state races.
"We're going to be emphasizing the importance of electing Democrats down the ballot," Clinton told reporters traveling with her on Saturday.
Obama has so far recorded television and radio ads for 17 Democratic candidates for the Senate and the House of Representatives, and a Democratic official said more are still to come.
He has also taped ads for candidates in three gubernatorial races, and endorsed about 150 candidates in state legislative races.
Obama has headlined rallies in Ohio, Pennsylvania, Illinois, Florida and North Carolina - and will head back to Florida on Friday.