This week, Rep. Michele Bachmann (R-Minn.) is watching her star fall nearly as fast as it rose after she announced her candidacy for president back in June. And that makes Wednesday’s debate at the Ronald Reagan Presidential Library in California a critical moment for her to reverse her fortunes once again.

Bachmann began her campaign at the first major debate of the year, in Manchester, N.H., where she dazzled viewers and pundits with a poised and charismatic performance that shattered most expectations. Her subsequent meteoric rise in the polls culminated in her victory at the Ames Straw Poll in Iowa last month — and the withdrawal of her main rival, former Minnesota governor Tim Pawlenty, the next day.

But Bachmann’s fortunes began turning the very day of the straw poll, when Texas Gov. Rick Perry announced his plans to seek the GOP presidential nomination. Perry instantly cut into Bachmann’s support within the tea party and conservative wings of the GOP, and his ten years of executive experience as a governor contrasted favorably with her two-and-a-half terms in the U.S. House. Bachmann’s national reputation as a tea party leader is also seen as a negative by some Republican voters who view her as too polarizing to win the general election against President Obama.

Bachmann’s slide culminated on the eve of Wednesday’s debate with a series of new public polls showing just how badly she is damaged. In a new Washington Post-ABC News poll published Tuesday, Bachmann drew the support of only 6 percent of all Republicans and GOP-leaning independents, falling behind not only Perry but also former Massachusetts governor Mitt Romney, former Alaska governor Sarah Palin (who is not running) and Rep. Ron Paul (Texas).

In addition, Bachmann’s campaign endured a shake-up this week with the departure of deputy campaign manager David Polyansky and the reassignment of campaign manager Ed Rollins to the role of campaign “adviser.” Campaign spokeswoman Alice Stewart said Polyansky’s departure was planned all along, and Rollins’s move was precipitated by health considerations. But Bachmann undoubtedly will be asked at Wednesday’s debate to address the perception that the campaign is struggling.

Viewers should also expect questioners from the NBC and Politico journalists who are hosting the debate to probe more deeply into Bachmann’s policy positions.

Bachmann has proven her mettle as a capable debater and soundbites master who can zing her opponents and rally the GOP’s conservative base with a seemingly infinite supply of one-line attacks against President Obama. But she has offered little in the way of substantive policy proposals. In the shadow of the 160-page jobs plan that Romney unveiled Tuesday, Bachmann must prove that she is more than a showhorse.

She must also seize as much airtime as possible — which could prove difficult, given the spotlight on Perry, who debuting at his first debate. With the presidential race shaping up as a two-man battle between Perry and Romney, Bachmann will be looking for opportunities to join that battle and regain her position in the top tier.