THE PACE quickens in Nicaragua. The government is offering to sign, at once, a regional peace treaty some of whose key details (on enforcement, for instance) have yet to be written. Some sort of negotiation goes on between the ruling Sandinistas and opposition leader Arturo Cruz over the terms on which he might take part in, and thereby legitimize, the Nov. 4 elections. In Washington, meanwhile, Congress juggles the fate of President Reagan's program to run an armed Nicaraguan insurgency against Managua.

For a couple of years now, Washington and Managua have been competing to demonstrate their support for the Latin democracies' Contadora initiative for peace in Central America. The Sandinistas' decision to embrace a treaty still in draft can be seen in that context. But the United States shouldnot simply be stumbling in embarrassment to find itself one-upped in this round. It should be welcoming Managua's opening, advising Contadora to complete the treaty and assuring the region it will support the security and political arrangements of its collective choice. Otherwise it risks hardening a widespread impression that its priority is not peace but to do in the Sandinistas.

Will the Sandinistas allow the Nov. 4 elections to be worthy of the name? The regime's assurances of procedural fairness must be measured against the continued mob assaults on Arturo Cruz's meetings -- a pattern that has kept him from organizing a campaign and that validates his request to postpone the vote a couple of months. Fortunately, the Latin and European democrats cultivated by the Sandinistas are still pressing them to open the elections. The foreign parties are also watching Mr. Cruz to ensure that his coalition does not make arbitrary demands. If the Sandinistas are half as confident of their popular appeal as they claim, they will make the right move soon.

The House has voted to cut off American funds for the Nicaraguan guerrillas. The Senate is unlikely to follow suit. The difference will be resolved in a context that has changed in the time that Congress has been addressing this issue. The new factor is the possibility that the insurgency is one factor inclining the Sandinistas to consider broadening the elections. The insurgents have agreed to impose a cease-fire if that happens. We are torn on this one, having consistently opposed the American role in the insurgency but seeing in the elections the single possible route to national reconciliation. Why do not the insurgents consider accepting a cease-fire right now to show they mean it?