WASHINGTON—The Biden administration has signaled that it could introduce gradual tax hikes to help pay for spending initiatives, drawing criticism from Republicans who worry that tax increases would hurt the economy. As part of his campaign promise, President Joe Biden proposed raising the federal corporate tax rate to 28 percent from the current 21 percent. And Treasury Secretary Janet Yellen in February indicated that the tax increases “would probably phase in slowly over time” and would help pay for Biden’s big spending agenda to be proposed later this year, including investments in infrastructure, clean energy, and education. According to Rep. Kevin Brady (R-Texas), a lead architect of the Tax Cuts and Jobs Act of 2017, Democrats will push for tax increases immediately after the signing of the $1.9 trillion relief package approved by the House Democrats on March 10. “Tax increases are coming, there’s no question about it,” Brady told Fox …