Mitt Romney will accept the Republican presidential nomination this week not only with a significant advantage in campaign cash but also a philosophical leg up on President Obama: Most Americans in a new Washington Post-ABC News poll want a shrunken federal government, and most believe Romney wants that too.

The debate isn't even close. Nearly six in 10 registered voters pick a "smaller government with fewer services" while just over a third want a "larger government with more services." Support for "smaller government" is up significantly in recent years, and marks a pivotal issue where voters view Obama as far out of step with public opinion. Nearly three quarters of voters believe Obama wants a bigger government, while almost as many say Romney wants a smaller federal government.

Romney wins the majority of voters who want a smaller government - seeing him as closer to their views - while Obama wins a majority of those who prefer bigger government. But overall, voters split near evenly in their support for president  - 47 percent for Romney and 46 percent for Obama - a reflection of the fact that Obama peels off nearly three in 10 "small government" voters while Romney wins support among only two in 10 "larger government voters.

The Republican national convention this week offers Romney a key opportunity to bring more of the small government majority to his side. He would lead Obama by double digits if he simply performed as well among smaller government voters as Obama does among those who want larger government.

Of course, the issue is not as simple as it looks, and the new poll finds challenges for Romney as small government principles clash with pragmatic realities. While most voters want a smaller government, majorities also support government spending to create jobs (vs. tax cuts) and lament an economic system that favors the wealthy (vs. onerous government regulations), neither of which is a good playing field for Romney.

Indeed, these are the very issues where Romney's and Obama's small government voters disagree the most. Nearly three quarters of small government voters who currently back Obama say "unfairness" is the bigger problem, while a similar number of Romney's small government supporters are more worried about "over-regulation of the free market." Among those who prefer small government, nearly six in 10 Obama backers say the government should spend more on roads, bridges and technology to create jobs; about the same portion of Romney backers prefer tax cuts.

The massive small government army may not be easy to muster after all.

The Post-ABC poll was conducted August 22-25 among a random national sample of 1,002 on landlines and cell phones. The margin of error for the full sample as well as the the sample of 857 registered voters is plus or minus four percentage points. Full interactive results are available here.

Peyton M. Craighill and Jon Cohen contributed to this report.