The chemistry between the two presidents is apparent

Part of it has to do with the growing importance of the Hispanic or Latino vote in the United States, most of which is made up of Mexicans.

But it is mainly because last year he won an election which ended 70 years of rule by the Institutional Revolutionary Party (PRI), an authoritarian political machine which was - at least until its final years in power - instinctively anti-American.

President Fox is quite different. His foreign minister, Jorge Castaneda, is an intellectual from the centre-left.

Friendly but frank

But overall, his administration has a flavour pleasing to US Republicans.

Mr Fox, who used to run Coca-Cola's operations in Mexico, talks the language of business.

Fox talked about immigration issues

He is a religious man who - as President Bush enjoys pointing out - likes to spend time on his ranch.

He talks about a partnership with the United States, and displays none of the prickly nationalism associated with the PRI.

For American politicians, President Fox is somebody to be seen with.

This goodwill means that Mr Fox has been able to be frank.

Controversy

Despite the warm tone of his speech to Congress that was liberally peppered with the word "trust", he was not afraid to mention all the most controversial issues in US-Mexico relations, including illegal drugs, the right of Mexican truckers to drive in the USA, and above all migration.

He wants a quick agreement to regularise the status of up to three-and-a-half million Mexicans living in the United States.

He also wants an expanded "guest worker" programme to allow others to cross the border temporarily.

There had been hopes that President Bush would announce the outlines of such a plan during the visit.

But some conservative Republicans are hostile to the idea, leaving Congressional Democrats as its biggest supporters.

The specifics will be difficult.

A new era

In general, though, there is no doubt that a new era in US-Mexican relations is under way.

Never have the two economies been so closely linked, thanks to the North American Free Trade Agreement.

Never has migration been discussed so openly and so frankly. And rarely have relations between the countries' political leaderships been so warm.

But although this new relationship will continue to be mainly of benefit to Mexicans, President Fox could in one way at least be its hapless victim.

The economic slowdown in the United States is having a big impact south of the border. Mr Fox will be lucky to avoid some blame for that.