TAMPA, Fla. – Republican Mitt Romney is stepping up for the most important speech of his life, to an audience of millions, after a rousing warm-up from a running mate who vowed the days of dodging painful budget choices will end if voters toss President Barack Obama from office.

Having grasped the nomination on his second try, after years spent cultivating this moment, Romney will use his speech Thursday night to introduce himself to a large portion of voters and claw for advantage in a race that could scarcely be any closer.

Romney hinted at the themes in a morning fundraising appeal emailed to supporters.