This mixed-methods research study examines the Co-requisite model, an intervention in developmental mathematics, for its impact on student affect leading to success in math. This research hypothesized that students enrolled in the Co-requisite model experience positive changes in four affective variables: internal mathematical identity, mathematical self-efficacy, mathematical mindset, and mathematical sense of belonging. A review of the literature revealed strong evidence that each of these variables is linked to success in developmental mathematics, that curricular interventions can mediate positive changes in affective characteristics, and that shifts in students' internal mathematical identity can occur through interventions that impact the other three variables. The empirical work for this study took place at a large suburban community college piloting the Co-requisite model. Hypothesis testing was conducted on data from pre- and post-surveys to determine: (1) correlations between course grades and each of the four affective variables; and (2) whether participation in the Co-requisite model led to changes in mathematical self-efficacy, mathematical mindset, and/or mathematical sense of belonging. Statistical analysis revealed two significant results: (1) a correlation between grades and mathematical self-efficacy at the end of the Co-requisite model; and (2) a change in mathematical sense of belonging. Both inductive and deductive coding methods were used to explain students' accounts of their experiences in the Co-requisite model with respect to affect. Extra time and space to build community emerged as themes. The extra time to gain understanding and the space to build community resulted in improved math performance and increased comfort and confidence for developmental math students. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]