On successive days this month, two democratic dissidents embraced by the Bush administration on opposite sides of the world were shoved into the same legal twilight zone, a virtual holding tank of menace and uncertainty that despots often find useful. Maria Corina Machado of Venezuela and Ayman Nour of Egypt were charged with crimes carrying heavy prison sentences; court proceedings were begun. But their final trial sessions then were left pending, in the case of Machado, or postponed for several months, in the case of Nour. That leaves them to twist in the wind this summer while their governments -- Hugo Chavez's Venezuela and Hosni Mubarak's Egypt -- measure the mettle of President Bush.

Bush may be the main reason each of these courageous dissidents faces prosecution. For Chavez and Mubarak, and for many Venezuelans and Egyptians, Machado and Nour are symbols of U.S. efforts to check the dismantling of democracy in Caracas and promote its introduction in Cairo. Machado, a 37-year-old single mother who met with Bush at the White House in May, is charged with treason because her nonpartisan election-monitoring organization accepted $31,000 from the National Endowment for Democracy. Nour, a 40-year-old lawyer who recently met Secretary of State Condoleezza Rice, is Egypt's leading proponent of a secular, liberal democracy and the only serious challenger in a presidential election Mubarak called to deflect U.S. demands for reform. He's charged with forging the petitions that allowed him to legalize his political party.

But Bush is also the reason Nour and Machado are not already in jail. Concerted pressure from Washington freed Nour after six weeks of detention without charge this year; further pressure has kept him on the street and on the ballot for the September election. Mubarak now understands that his future relationship with Washington could turn on whether the election is judged sufficiently free and fair. Since almost all the rest of the Egyptian opposition has declared a boycott, Nour's participation is critical.

Bush's high-profile meeting with Machado enraged Chavez, who ordered up her prosecution 17 months ago on his weekly television show. But it sent the message that her conviction, along with the three other members of her Sumate group, could risk an irreversible rupture in a relationship in which Chavez has sought to preserve an option of accord. A prison sentence would provide U.S. diplomats with a powerful argument for persuading other Latin American governments to recognize Venezuela's violations of the region's democratic charter.

So Machado and Nour wait, while the strongmen measure Washington's reaction and calibrate their own next steps accordingly. Any ambiguity about the political nature of the two court cases disappeared long ago. One of Nour's accusers recently testified that he had been coerced to parrot false accusations by Mubarak's secret police. Chavez's prosecutor has breezily ignored rulings by the Venezuelan Supreme Court.

"Our fear is that having rejected most of our proofs, they can handle the trial with sort of a fast track . . . they could also keep it pending and have us terribly pressed meanwhile," Machado wrote in an e-mail to me last week. "Frankly, given the way they have violated the due process up to this point, anything could happen."

As usual, Mubarak's strategy is clunky and transparent. He hopes Washington will swallow a lopsided election in which he trounces Nour; a week or two later he can order a favorite judge, Abdel Salam Gomaa, to convict the democrat. (Months ago a senior Egyptian official told me that Nour's trial would be delayed, following an opening session, until after the election; sure enough that's exactly what Gomaa's "independent court" decided.) Nour would then be barred from future elections, when the 77-year-old Mubarak will no longer be a candidate; a potential rival to his 41-year-old son and political heir would be eliminated.

Chavez's calculations are less clear, and possibly more fluid. He could choose to condemn Machado and her colleagues as American lackeys and traitors in a full-blown show trial, and thereby try to propel himself in one leap past the fading Fidel Castro to leadership of Latin America's undemocratic left. Or he could pardon the democrats, perhaps after seeking Washington's agreement to ramp down its own diplomatic campaign against him.

In short, Bush's response to these two trials will play a large role in shaping the outcome of what may be the most important ongoing battles over democracy in the world, outside of Iraq. The charges have been leveled, the prosecutors have spoken: Now Hosni Mubarak and Hugo Chavez await George Bush's defense.