Walker on the issues

Foreign policy: Walker has faulted President Obama for what he calls a lack of a strategy in dealing with the Islamic State in Iraq and the Levant and said he would not rule out sending U.S. ground troops to Syria to confront the group. "We're not going to wait until they bring the fight to us — we're going to bring the fight to them, and fight on their soil," he said. He has said he would cancel any deal the Obama administration makes with Iran to curtail its nuclear program; this drew a rebuke from Obama, who told Walker to "bone up" on foreign policy. Walker similarly takes issue with the president by saying he would provide arms to Ukraine to fight Russian-backed rebels in that country, and he opposes Obama's warming of ties with Cuba.

Immigration: A pathway to citizenship "makes sense," Walker used to say, but he has shifted his position recently: He now opposes citizenship for those in the country illegally and favors greater border security and enforcement of ­immigration laws, which has led critics to accuse him of changing his tune to attract more conservative voters in early nominating states like Iowa. Rather than embrace deportation, he has indicated in private gatherings that he supports giving immigrants in the country illegally an opportunity to earn legal status — but not citizenship.

Environment: Walker has not taken a clear position on ­climate change. He has proposed giving many of the ­powers of the Environmental Protection Agency to the states. As governor, he has proposed cutting funding for clean energy and for other environmental programs, and he has opposed the Obama administration's efforts to reduce the carbon footprint of the nation's power-generation sector.

Same-sex marriage: Opposing same-sex marriage, Walker says he believes in "marriage between one man and one woman." As a state lawmaker before he became governor, he supported a ban on same-sex unions.

Education: Two years ago, Walker called on the Wisconsin Legislature to repeal and replace the Common Core national educational standards, which were meant to raise proficiency in math and English but are seen by many conservatives as a federal overreach. But he "showed tacit support for Common Core during most of his first term" as governor, the PolitiFact fact-checking website found. Recently, Walker has moved to weaken tenure for professors in the University of Wisconsin system and to cut its funding; in his budget this year, he recommended changing the system's mission "to meet the state's workforce needs" — though he later backtracked on that language, calling it a "drafting error."

Economy and budget: Walker made his name trying to curtail spending, largely by taking on public-sector unions. He pushed through more than $500 million in tax cuts last year, although Wisconsin faced a nearly $300 million deficit this year and missed a $108 million payment on its debt, incurring additional costs. He has not detailed his plans for the federal tax system, although he is likely to call for broad-based tax cuts. In March, he said abolishing the federal tax system "sounds pretty tempting," but he did not fully endorse the idea, which is more of a fringe position on the right. He has promised to pursue major changes in federal entitlement programs. Walker is also expected to focus on job creation.

New York Times