The presidential race has been stable for months but not in a way favorable to Mitt Romney. On his best days, Romney is even with President Obama. On his worst, Romney is a few points behind.

This dynamic has not been changed through advertising. More money has been spent on TV ads in the general election so far this year than during the entire 2008 presidential election. More money was spent this past July on ads in Charlotte, Orlando and Columbus, Ohio, than was spent in those markets in October 2008. But opinion seems settled and difficult to budge.

The selection of Paul Ryan did not change the structure of the race. What initially seemed like an ideological choice — previewing a shift in campaign strategy and content — now seems like a more personal decision. Romney is comfortable with Ryan and an improved candidate in his presence. But Romney’s message is untouched by his running mate’s revolutionary fiscal realism. Romney chose Ryan, not Ryanism.

Romney’s convention speech did not change the unfavorable stability of the campaign. Romney softened his image through biography; he did not broaden his appeal with unexpected outreach. There were no innovative policy initiatives directed toward Hispanics or suburban women. The speech was humanizing but ideologically uncreative.

With less than two months until the election, Romney is left with dwindling opportunities to reshape the dynamic of the race. This places extraordinary pressure on him in the presidential debates that commence on Oct. 3. He was an able debater during the Republican primaries. Obama is a weaker debater than his reputation — often professorial and elliptical. But Romney has the harder task. He must do more than hold his own. He will need to shake and shift public attitudes. And it is not easy to be aggressive during a debate without appearing overbearing or desperate.

This analysis requires an admission. Obama’s political strategy has generally worked. The president could not run on his economic performance. So he has turned the race into an ideological contest that he has a better chance of winning. His convention speech — equally light on creative policy — emphasized the choice between Democratic community and Republican selfishness. The Democratic convention (with the exception of Bill Clinton’s throwback moderation) was designed to energize social liberals and economic populists while trying to destroy Romney as a viable alternative.

This approach to politics is not pretty. If it succeeds, we will see a lot more early, scorched-earth negative attacks and purposeful ideological polarization in American campaigns. Quite a legacy for Obama to leave.

But Romney has made his contribution to the success of Obama’s strategy. The Democratic convention also included an aggressive outreach to Hispanic voters — enabled by Romney’s alienation of this group during the Republican primaries. The policy of “self-deportation” has pushed a community heavy with social conservatives and entrepreneurs toward the party of Sandra Fluke and Elizabeth Warren. Quite a legacy for Romney to leave.

While Obama’s approach is currently succeeding, it has not yet succeeded. A base strategy requires a party’s base to turn out on Election Day. For Obama, Latinos, single women and younger voters must become likely voters. And here the Obama campaign should be concerned. Levels of enthusiasm in the Obama coalition are lower than four years ago. Just before the 2008 election, for example, 78 percent of voters ages 18 to 29 expressed a firm intention to vote. Now that figure is 58 percent. Democrats are engaged in a serious get-out-the-vote effort. But in politics, as in courtship, organization is usually a poor substitute for passion.

And it is also possible that bad economic news will be a sodden blanket that weighs down Obama’s support among all groups. Job growth is historically weak. At the August pace of job creation, according to Diana Furchtgott-Roth of the Manhattan Institute, America will reach 6 percent unemployment in 32 years. Under normal circumstances, this would recommend a presidential pivot to an aggressive job creation agenda. But Obama’s convention speech was pivotless. He offered a stay-the-course message in a faltering economy. These objective conditions may place an upward limit on Obama’s support — a ceiling somewhere lower than 50 percent of the vote.

This remains a close presidential contest, in which Obama has significant vulnerabilities. But Romney does not appear to have a route to victory that allows him to coast. If he plays not to lose, he seems likely to lose.