Is a prosecutor entitled to use improper tactics in response to tactics of defense counsel?

United States v. Young, 470 U.S. 1, 12-13 (1985). While a prosecutor may fairly rebut defense counsel's contentions, United States v. Bagley, 772 F.2d 482, 494 (9th Cir. 1985), he or she is not entitled to use improper tactics in response to tactics of defense counsel, Young, 470 U.S. at 7-9. However, "a court should not lightly infer that a prosecutor intends an ambiguous remark to have its most damaging meaning or that a jury, sitting through lengthy exhortation, will draw that meaning from the plethora of less damaging interpretations." Donnelly, 416 U.S. at 647.