NewsMax offers a roundup of Hillary being to the "right" of Bush on immigration matters: "Hillary Eyeing Immigration as Top 2008 Issue". There's no outright statement from her saying if she ran she'd make it a key part of her campaign, but some of the things she's said might make people think she's got that in mind. If she makes reducing illegal immigration a key part of her campaign, who would support her and who would oppose her?

On the opposition side would be the de facto left-right alliance that supports massive legal immigration and massive illegal immigration. You can see this alliance at work in the opposition to Arizona's Prop. 200 or in the categorized list of the 400 companies and organizations that support the AgJobs amnesty program. The members of this alliance include:

• The media. They smear those who oppose illegal immigration as "nativists", they write editorials supporting illegal aliens taking education dollars from U.S. citizens, they publish "pro-illegal immigration puff pieces", they ignore the elephant in the room, and on and on.
• Big business: banks, growers, money transfer companies, sweatshop operators, etc. etc. It's all about the "cheap" labor and the new consumers.
• The Ethnic Industry. All of these are far-left, and many are quite simply anti-American. It includes college professors, politicians trying to increase their power by bringing in new constituents of the same race, and "grassroots" organizations like MALDEF, NCLR, and LULAC. Believe it or not, behind many of these groups you'll find Ford Foundation money. For instance, UCLA published a "study" advocating voting rights for illegal aliens. The school at UCLA it came from was founded by the Ford Foundation, and the "study" was written by a former president of MALDEF. MALDEF had been more or less created out of whole cloth by the Ford Foundation. (On the other side, 47% of Arizona Hispanics voted for Prop. 200)
• Immigration lawyers. Here's a tangible example involving Rep. Chris Cannon (R-UT). After reading about his funding, see this.
• The government of Mexico. Partial control of our immigration system has been turned over to a foreign government; what Mexico wants is apparently more important than what American citizens want. For its part, Mexico receives almost as much from remittances (money sent home from workers in the U.S.) as it does from oil; remittances are Mexico's second greatest source of income. Even if someone is ignorant of our history with Mexico, it should come as no surprise that they claim part of our population as their own, they threaten us with civil unrest if they don't get their way, their agents criss-cross the U.S. selling ID cards to their citizens despite many or most of the recipients being here illegally and despite the FBI calling those ID cards a terrorist threat, and they are allowed to or encouraged to meddle in our laws.
• Non-corrupt ideologues. A small percentage of Americans support illegal immigration despite not being paid to do so. Almost all of them are far- or very far-left. For a small example, see the comments here (especially those by 'm berst') or see this thread. Some libertarians support Open Borders, but even Michael Badnarik opposes illegal immigration despite supporting massive legal immigration.

What about the other side of the ledger?

Here's who Hillary would get support from:

• The 75% of the American public who support a reduction of illegal immigration. (Pew PDF)

If handled correctly, I think she'd find that the support would far outweigh the opposition, despite the opposition's clout. For every member of the far left she lost, she'd gain at least one and probably more from the center or the right.

In the words of the Sacramento Bee's Daniel Weintraub: