On Wednesday, Republican presidential nominee Mitt Romney dismissed concerns over a recent glut of bad swing-state polling that has left him in trouble in the near must-win: Ohio.

"I’m very pleased with some polls, less so with other polls, but frankly at this early stage, polls go up, polls go down," Romney told ABC's David Muir after a day of round-the-clock campaigning in the Buckeye State. 

Romney will spend the next 40 days campaigning there tirelessly, because the state offers him one of his few clear paths to electoral college victory. Though he only trails by an average of 4 points in national polling, he'll be hard-pressed to pick up the electoral college votes he needs without Ohio. 

With that in mind, we took a look at where Romney is facing the biggest challenges — and what happens if he doesn't overcome them.

Florida has become the most troubling state for Romney in recent days, going from pure toss-up to trending more in Obama's direction.

Obama holds about a 3-point lead over Romney in the RealClearPolitics average of the state, despite the fact that the Republican National Convention was held in Tampa at the end of last month. 

This map shows why Florida is a virtual must-win for Romney. If he loses, he would have to take swing states Ohio, Iowa, New Hampshire, Colorado, Wisconsin, Nevada and Virginia to get past 270. That's an extremely illogical path to victory — especially because two of those states (Ohio and Wisconsin) have moved to the "lean Obama" column on the RCP average.