Messina saw good signs all over, saying, ‘‘We’re either tied or in the lead in every battleground state 45 days out. I think you will see a tightening in the national polls going forward.’’

Ryan, campaigning in Miami’s Little Havana neighborhood, reinforced Romney’s argument that Obama hasn’t been able to make needed changes in Washington, poking at the president’s recent comment that it’s hard to change Washington from the inside without mobilizing public pressure on Congress from the outside.

‘‘Why do we send presidents to the White House in the first place?’’ Ryan asked. ‘‘We send presidents to change and fix the mess in Washington, and if this president has admitted that he can’t change Washington, then you know what? We need to change presidents.’’

He also faulted Obama for a ‘‘policy of appeasement’’ toward the Castro regime in Cuba, saying all the president had done was ‘‘reward more despotism.’’

Obama has eased restrictions to allow Americans to travel to Cuba and to let Cuban-Americans to send money to family on the island. But the president has stopped well-short of discussing lifting the 50-year-old economic embargo, which is widely viewed in Latin America as a failure and has complicated U.S. relationships in the region.

Campaign spokeswoman Jenn Psaki said the president had supported democracy movements on the island and worked to give people there more say in their futures.

In an appearance in Orlando, not far from Florida’s space coast, Ryan criticized the president for putting the U.S. space program ‘‘on a path where we are conceding our global position as the unequivocal leader in space.’’ The Obama campaign responded that Ryan has proposed deep cuts in spending for space exploration.

Underscoring the importance of grass-roots efforts in the campaign’s final days, Biden rallied union workers at a Teamsters union hall in Manchester, N.H., saying their organizing work would be the ‘‘antidote’’ to millions spent on advertising by Republican-leaning super PACs.

Biden said it was because of unions that the U.S. has a strong middle class, and he accused Romney and Ryan of having ‘‘a completely different value set, a completely different vision.’’

‘‘They’re doubling down on everything that caused the economic crisis in the first place,’’ he said.

The GOP nominee is feeling fundraising pressure: Last month, for the first time in four months, Obama and the Democratic Party raised more than Romney and the Republican Party, $114 million to $111.6 million.

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