Barack Obama on Wednesday pointed out the differences between John McCain’s historical positions on immigration and the policies advocated by the Republican party platform adopted at the party’s convention last week, using those differences to question the Republican nominee’s commitment to changing Washington.

The Republican platform generally takes a hard stance on immigration, and specifically opposes permitting states to “flout the federal law barring them from giving in-state tuition rates” to illegal immigrants.

Senator McCain, by contrast, has supported Congressional efforts to overhaul immigration laws, including a measure known as the Dream Act that was included in a bill that died in the Senate last summer. That provision would have set out a path to legal residency for some illegal immigrants who had been enrolled for at least two years in college, and would have made them eligible for federal student-loan and Work-Study programs.

Since announcing his candidacy last fall, Mr. McCain has shifted his rhetoric to emphasize improving border security before turning to issues like education benefits for undocumented students, although a key McCain adviser said just before the convention that the senator continues to support such efforts.

From the campaign trail yesterday, Senator Obama argued that Senator McCain had failed to stand firm in the face of opposition from his own party, CNN reported.

“I know Senator McCain used to buck his party by fighting for comprehensive reform, and I admired him for it,” CNN quoted Senator Obama as saying about Mr. McCain’s immigration stance.

But, the Democratic candidate added, “When it came time to write his party’s platform, comprehensive reform never made it in. So you’ve got to ask yourself: If Senator McCain won’t stand up to opponents of reform at his own convention, how can you trust him to stand up for change in Washington?”