The unified Democratic front now facing Mayor Bloomberg raises the stakes in this mayoral election while also raising the real possibility the mayor could lose on the basis of demographics and turnout. There is no room for false confidence on the Republican front.

The fact that Fernando Ferrer exceeded his primary-eve poll numbers by eight percentage points on an Election Day characterized by low turnout offers a glimpse of the dynamics which could come into play this Election Day: depressed voter participation in the city overall while Hispanic voters turn out in heavy numbers for their first general-election candidate for mayor.

Mayor Bloomberg is not the kind of political leader who inspires passionate allies or enemies; even the normally loquaciously hateful rhetoric of Al Sharpton is subdued when discussing the current occupant of City Hall. Mr. Ferrer and the president of Manhattan, C. Virginia Fields, are on the record as saying that Mr. Bloomberg is a better mayor than his predecessor, Mayor Giuliani. But in the pursuit of building back the party’s credibility, Democrats are less likely to be so sentimental when it comes to pulling the lever on Election Day.

The basic problem remains that in a city with a 5-to-1 Democratic registration advantage, virtually any Democratic candidate begins the election with more than 40% of the vote. Republicans, on the other hand, have very little margin for error.

The local electoral demographic trends are troubling for Mr. Bloomberg as well. In last year’s presidential election, nearly 200,000 new voters turned out in New York City. Almost all of them were first-time immigrant voters, concentrated heavily in areas such as the Bronx. An analysis by Barnard College’s New Americans Exit Poll explained that “the foreign-born voter in New York is more likely to be a working-class person of color, female and living in a family with young children at home” – in other words, just the kind of voter who could see Mr. Ferrer’s campaign as a crusade.

In contrast, the must-win areas of the Republican base such as Staten Island have seen voter participation decline in recent years. In these GOP stalwart sections, the challenge is not just to win the percentage game decisively; it is a matter of getting high turnout. With Republican leaders such as James Oddo frequently frustrated by the mayor (in an interview earlier this year, Mr. Oddo told me that “my relationship as a Republican City Council member with City Hall couldn’t get any worse with a Ferrer or Miller regime”) the chance that these local leaders will fully deploy their forces in an effort to get out the vote on behalf of Mr. Bloomberg is unlikely.

In addition, while Mr. Bloomberg’s volunteer headquarters in Manhattan and Borough Park have healthy numbers of volunteers, other district field offices – such as in Bayside, Queens – are comparatively empty to date. This bodes badly for turnout among the Republican base – missing Bayside votes cannot be compensated for by high Bloomberg ratios on the Upper West Side.

It is true, of course, that the mayor has been dominating the polls since he began his unprecedented advertising blitz in the spring. But while shifts in perceptions can change poll numbers, they do not necessarily directly impact turnout numbers on Election Day.

Nowhere will this be more evident than in Mr. Bloomberg’s 45% support among African-Americans and Hispanic voters in recent polls. The basic gravity of New York elections will begin to reassert itself now that the Democratic nominee has been chosen. Mr. Bloomberg’s African-American support is likely to dip down toward 35%, while his Hispanic support can be expected to hit the low 20s – still respectable against a Hispanic candidate, but not enough to sustain Mr. Bloomberg’s current overall margin. This will lead local talking heads to pontificate on the Ferrer surge in the coming weeks, compounding the perception of shifting momentum, which will in turn help solidify Democratic ranks.

But Mr. Bloomberg still has many solid advantages beyond his competence in office and the impact of a $100 million campaign. The pathetic Democratic primary turnout – just 17%, about half of what it was four years ago – calls into question how many of the missing voters are Democrats sitting out the primary with the intention of casting their fall ballot for Mr. Bloomberg. Against this backdrop, Mr. Ferrer’s 39.95% of the primary vote is even less impressive, giving him the demonstrated support of just 6.8% of total Democrats citywide.

There is also the question of how intensely Mr. Ferrer intends to reach beyond his base as he approaches the general election. Usually, with the primary fight over, the victor begins to center his campaign, but Mr. Ferrer’s speech was full of the rhetoric of the liberal left. There is a personal affection for Mr. Ferrer among many members of the New York political community, but his political positions on issues such as tax increases and non-citizen voting are far to the left of the average New York voter. Whether Mr. Bloomberg will be willing to point out these differences in tough but substantive ads has yet to be seen, but the gentlemanly mayor generally prefers to avoid this rough and tumble of politics.

The question for the New York City 2005 mayoral election is whether Mr. Ferrer will be able to rally his base while winning over enough white, moderate middle-class voters to put together a broadly popular campaign. Mr. Bloomberg’s strong showing in recent polls has lulled many supporters into concluding that the election is essentially over, but a unified Democratic party backed with high turnout in key areas, combined with an unmotivated Republican base, could provide a nasty surprise for the mayor this November.