President Obama rallies Democrats

Republicans are expected to make big gains in the congressional ballots and President Obama must limit the damage by mobilisng a coalition of young voters and the Democratic party's progressive base that won him the White House in 2008.

The Pennsylvania crowd was estimated at over 18,000 by city officials, the rally organizers said.

In a packed schedule Obama will travel to Florida on today to campaign for Democrats, take part in two townhall style events designed to address ordinary Americans during the week, visit Delaware on Friday, and stump for his party again in Massachusetts on Saturday.

He will also host a meeting at the White House on Monday morning to showcase his push for additional infrastructure spending to boost hiring and communicate that he understands the fear of American households over unemployment.