PATRICK BUCHANAN'S bid to defeat George Bush in the New Hampshire presidential primary will depend heavily on three issues: taxes, foreign aid, and a strong sense of American nationalism.Mr. Buchanan, a conservative newspaper and TV commentator with close ties to Ronald Reagan and Richard Nixon, launched his campaign Tuesday just 10 weeks before New Hampshire voters go to the polls. If Buchanan does well there - experts say his vote could range from 10 percent to 40 percent - he vows to carry the fight against Bush across the country. His long-term goal: make the president quit the race before the Republican National Convention. At the very outset, Buchanan is tapping into the anger and fear that have grown in the American electorate as the recession wipes out millions of jobs, including thousands in New Hampshire. Attacking foreign aid, for example, Buchanan asks why the United States government still sends billions abroad while facing a $4 trillion debt, growing unemployment, and an unbalanced budget at home. Critics charge that Buchanan's "America First" theme smacks of 1930s-style isolationism, which historians say laid the groundwork for World War II. But Buchanan responds that unlike Bush, whom he chides as a "globalist," Buchanan is a "nationalist" ready to stand up for American workers. "Today, we call for a new patriotism, where Americans begin to put the needs of Americans first, for a new nationalism where in every negotiation ... the American side seeks advantage and victory for the United States," Buchanan says. "It is time to phase out foreign aid and to start looking out for the forgotten Americans right here in the United States." Although Buchanan calls Bush "a decent, honorable, patriotic guy" who risked his life as a Navy pilot during World War II, Buchanan says Bush "is yesterday, and we are tomorrow." Echoing some Democrats, who criticize Bush as a prep-school elitist, Buchanan says his campaign is for "the working people and the middle class of both parties." He criticizes congressional Democrats as "ossified" and the "ruling class" in the White House as "out of touch." "Why am I running?" he asks. "Because we Republicans can no longer say it is all the liberals' fault. It was not some liberal Democrat who declared, 'Read my lips, no new taxes,' and then broke his word to cut a seedy backroom deal with the big spenders on Capitol Hill.... No, that was done by the man in whom we placed our confidence and our trust, and who then turned their backs on us and walked away from us." While Bush will be heavily favored in this political warfare with the right wing of his party, Buchanan could score some painful hits before this battle is over. New Hampshire is an ideal battleground for Buchanan. It often supports underdogs. And in late 1991, its economy is ravaged by joblessness, home foreclosures, and a weakened banking system. Buchanan, known for his pugnaciousness on TV talk shows such as CNN's "Crossfire," could prove to be a worthy opponent. Communications is his business. He wrote speeches for Richard Nixon (1969-72) and was the director of communications for Ronald Reagan's White House (1985-87). Born in Washington, D.C., he comes from a Roman Catholic background, with schooling in Catholic schools, including Georgetown University. He has said: "My views, my values, my beliefs were shaped by being a member of an Irish-Catholic conservative family of nine children. The church taught, and I think, correctly, that the great ideological enemy of Christianity and Catholicism was communism." Buchanan's campaign carries the torch for growing numbers of conservatives who feel Bush has abandoned their cause.