Democratic President Barrack Obama and Republican challenger Mitt Romney flew out this key western battleground state Sunday and headed east to rally forces for Tuesday's vote.

The president finished his 13th and last pre-election trip to Colorado with a rally of 20,000 cheering fans in this suburb of 330,000, east of Denver.

Aurora is the same city where, 100 days ago, Obama consoled family members and victims after one of the worst mass shootings in U.S. history that saw 12 killed and 58 injured in a midnight Batman movie showing.

"Unfortunately, the people of this town understand what it means to grieve better than most," Obama said.

A boisterous crowd braved cool temperatures in the low 5 Celsius degrees to hear the president connect them with victims of superstorm Sandy, which five days ago killed more than 100, left 8.5 million without power, and caused an estimated 30 to 50 billion dollars in damage.

Romney also criss-crossed the swing state at the weekend, with speeches Saturday to crowds totaling 22,000 in Englewood and Colorado Springs, where he repeated his attacks on the president's record in office.

Thursday in Boulder, the president told 10,000 supporters that four years ago after then Republican president George Bush's policies, he inherited a devastated economic system that has taken time to rebuild.

"FEMA (The Federal Emergency Management Administration) is something we need," said 75-year-old retired teacher Harriet Boonin, who opposes the federal cutbacks on education and emergency relief proposed by Romney.

Colorado and Nevada are considered the top two western "battleground states" that, with several other hotly contested contests, mostly in the east, will decide the presidential election. Those states include Ohio, Florida, Virginia, Pennsylvania, North Carolina, New Hampshire, Minnesota and Wisconsin.

In a highly reputable ABC/Wall Street Journal poll released over the weekend, President Obama leads Colorado 47-46 percent. The polls in Colorado have been neck and neck since Obama's poor debate performance in Denver on Oct. 3.

"They both keep saying the same thing," said Romney supporter Todd Borning, 38, an electrician from Gunbarrel, Colorado, who heard the president's speech.

"Most people are so set - it's like changing your mind on God," Borning said, who was upset that Obama's celebrated saving of the U.S. auto industry included insistence that General Motors manufacture the Chevy Volt, a hybrid electronic car.

"Government shouldn't be telling the private sector what to do," he said.

The federal bailout of the American auto industry in Detroit is a key campaign issue working to the Democrat's advantage in Ohio, a state heavy in manufacturing.

As both candidates flew east with Monday rallies scheduled in Ohio and other battleground states, political television advertising in Colorado reached record proportions - broadcasting virtually nonstop emotional appeals that targeted a small percentage of undecided voters.

While Obama's donations for advertising, mostly in small amounts from many individuals, outspent Romney 29 million dollars to 17 million, private, extremely wealthy contributors allowed the challenger to outspend the president 42-to-38 million dollars, according to data released Monday by the National Journal, which monitors campaign spending across the country.

In Colorado, "superpac" committees, formed by wealthy political operatives and whose individual donors remain anonymous, gave Romney 25 million dollars and only 9 million dollars to the president.

This advertising trend is similar nationally, where Romney spent 1.022 billion dollars, compared to Obama's 931.47 million dollars, according to Journal statistics. About half of Romney's money comes from superpacs.

"The superpacs have made up for the Republican's lack of smaller contributions," said Russ Choma, National Journal money and politics reporter. "We've seen this across the country," he said.

Another national trend visible in Colorado is that rural American areas will vote Republican while urban areas such as Denver and Boulder tend to be Democrat.

An exception is the city of Colorado Springs, called the "Most Conservative" city in America a few years ago and home to more than 100 Christian groups.

Both in Colorado and nationally, women, blacks and Latinos are expected to support the president, while white men are expected to favor Romney.