President Barack Obama has campaigned in the battleground state of Nevada for Hillary Clinton, but spent most of his time talking about the state's Senate race.
Democrats badly want to get back control of the Republican-controlled Senate in the November 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 US 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 per cent support to Trump's 41.3 per cent, 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.
"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.
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.
