Candidates traditionally get a bounce in the polls from political conventions, though there is little sign that Romney improved his standing after the Republican convention in Tampa, Florida. Once dramatic events for selecting candidates and debating issues, political conventions are now carefully scripted shows put on by the parties with little spontaneity _ making them less compelling programming for television viewers.

Tuesday's other major speaker during prime television time was San Antonio Mayor Julian Castro, who was delivering the high-profile keynote address.  A rising star in the party, Castro is of Mexican-American descent and his selection highlights the importance given to Hispanic voters in the race.

Castro, in excerpts of the speech released in advance, said Obama “knows better than anyone there's more hard work to do.”  He said the United States is making progress “despite incredible odds and united Republican opposition.”

He said Republican economic theories have been tested and failed. “Mitt Romney just doesn't get it,” he said. 

He was preceded by a series of speakers denouncing Romney. Senate Majority Leader Harry Reid of Nevada repeated attacks about Romney's refusal to release years of past federal income tax returns.

“Never in modern American history has a presidential candidate tried so hard to hide himself from the people he hopes to serve,” he said.

Other convention highlights include Wednesday's roll call votes formally nominating Obama and Vice President Joe Biden, and a speech by Bill Clinton, the popular former president. The climax will be Obama's acceptance speech at a 74,000-seat football stadium on Thursday.

That speech will seek to recapture the grandeur of Obama's acceptance address in a Colorado football stadium four years ago. At the time, the United States was in the midst of a devastating financial crisis while unpopular wars were dragging on in Iraq and Afghanistan.  Obama _ young, magnetic and eloquent _ captured the imagination of many Americans as the first black nominee of a major party. He promised a fresh start after eight years of George W. Bush's presidency and new hope for the economy.

Obama did withdraw U.S. combat troops from Iraq and the United States emerged from the recession. But economic growth has been tepid and unemployment is high at 8.3 percent.  Though he stepped up drone strikes on suspected terrorists and gave the order that led to the killing of Osama bin Laden, Republicans cast him as a weak leader. He won congressional approval of an overhaul of the U.S health care system, but his plan remains largely unpopular. Meanwhile, some Democrats have been disappointed by Obama's failure to close the prison at Guantanamo Bay, Cuba, and what they see as lackluster action on issues such as climate change and immigration reform.

Republicans have been pressing a question made popular during Republican Ronald Reagan's successful campaign against incumbent President Jimmy Carter, asking voters if they are better off than they had been four years ago.  Republicans released a web video that interspersed images of Obama and the economy's weak performance with slightly out-of-focus video clips of Carter discussing the country's economic woes when he sat in the White House more than 30 years ago.

Obama has also been invoking unpopular former presidents, arguing that Romney plans to reprise Bush's policies.

The election will allow voters to choose between contrasting visions of the role of government.  Romney's Republicans, increasingly guided by the anti-tax tea party movement, want to minimize the role of government, which it sees as an obstacle to enterprise and liberty. Obama's Democrats see government as a potential force for good, helping the downtrodden and providing the education and infrastructure needed to help the country prosper.

The campaign promises to be the most expensive ever and Republicans already have a financial advantage. Romney's presidential campaign raised at least $100 million in August for the third consecutive month. Two people familiar with the early numbers spoke on condition of anonymity because they were not authorized to share internal campaign matters. The amount includes money raised by the national Republican Party and will be publicly released next week.

Obama's advisers are now publicly acknowledging the president will likely be outspent in this election.

Obama spent part of Tuesday addressing college students _ an important part of his base _ in Norfolk, Virginia, a key tossup state. He urged them not to forget him despite difficult times.

Republicans are “counting on you, maybe not to vote for Romney, but they're counting on you to feel discouraged,” he said.

Obama said he and his two daughters would watch his wife's convention speech on television. “And I'm going to try not to let them see their daddy cry, because when Michelle starts talking I start getting all misty.” (AP)